Optical switch cascading system and method with variable incidence angle correction

ABSTRACT

The present invention is an efficient system and method for cascading optical switches. A plurality of cascaded optical switches form a cascaded optical switch fabric and direct an optical signal beam from one of the plurality of optical switches to another of the plurality of optical switches. In one embodiment of the present invention, a variable incidence corrective device is included in a cascaded optical switch fabric. The incidence corrective device directs an optical signal beam in a shallow angle so that it strikes the next optical switch at a corrected incidence angle. A corrected incidence angle permits an optical signal beam to be forwarded at a relatively shallow angle to an optical switch located in a relatively close proximity on the optical switch fabric. The present invention also provides for refocusing of spreading optical signal beams and mitigation of signal loss.

FIELD OF THE INVENTION

The present invention relates to the field of optical signal beammanipulation and propagation. More particularly, the present inventionrelates to a system and method to facilitate cascaded switching ofoptical signal beams with incidence angle correction and beam spreadcorrection.

BACKGROUND OF THE INVENTION

Systems utilizing various types of signals to represent information havemade a significant contribution towards the advancement of modernsociety and are utilized in a number of applications to achieveadvantageous results. Numerous technologies such as digital computers,calculators, audio devices, video equipment, and telephone systemsfacilitate increased productivity and cost reduction in analyzing andcommunicating information in most areas of business, science, educationand entertainment. Advanced optical signal based technologies offer thepotential for rapid processing and communication of large amounts ofdata associated with a variety of activities. The optical based systemstypically involve signal manipulation by signal switching operations.However, a number of optical signal beam manipulation problemsassociated with achieving optimal incidence angles and/or minimaloptical signal beam spreading often make traditional control of thesignals difficult or impractical.

To obtain maximized performance from information systems it is usuallycritical for the information to be processed and communicated rapidlyand reliably. Encoding information in optical signals offers thepotential for manipulation and conveyance of significant amounts ofinformation very quickly. For example, most optical systems havesignificant potential bandwidth capacity for processing andcommunicating a large quantity of data per unit of time. While sometypes of optical signal beam controls are relatively simple and easy toaccomplish such as transmission of an optical signal beam along aconfined single waveguide path (e.g., formed by a fiber optic cablestrand), other types of optical signal beam control such as dynamicallydirecting an optical signal beam along various paths are relativelydifficult.

The ability to control the manipulation and propagation of opticalsignal beams through a variety of paths usually involves theimplementation of switching elements. Switching elements provide amechanism for directing the optical signal beam to a particulardestination, often redirecting the signals along particular designatedpaths. However, the resources involved in manufacturing attempts at asingle switch capable of redirecting optical signals goes up as thenumber of potential paths increase. Some traditional switching networksystem configurations attempt to forward a signal to multiple potentialdestinations by utilizing a network of discrete limited switchesconnected with external cabling. These traditional attempts typicallyconsume significant resources to manufacture each discrete switch oflimited capability and additional resources to “wire” them together(e.g., connect cables between each individual limited switch). Anothertraditional approaches to switching operations involves converting anoptical signal into an electrical signal and vise versa. Theseapproaches are usually slow and require significant resources toimplement.

Switching optical signal beams typically involves significant challengesfor single switches capable of directing optical signal beams along avariety of paths. The nature of light propagation gives rise to a numberof complications that can potentially limit or impede the ability todirect an optical signal beam to a particular destination. Cumulativedetrimental effects associated with repeated redirection of opticalsignals tend to limit the practical utilization of traditional opticalswitches for applications involving significant control flexibility. Therelationship of incidence angles and output angles can give rise todetrimental effects in situations where angles become cumulativelydeeper each time an optical switch redirects an optical signal beam.Large incidence angles often prevent the propagation of an opticalsignal beam to a nearby device at an optimal incidence angle. Anotherpotential detrimental impact of repeated redirection of an opticalsignal beam is deteriorating divergence or spread of the optical signalbeam. Each time an optical beam is switched it spreads and a portion ofthe signal energy is lost. Theses energy losses are typically cumulativeand have adverse impacts on interpreting the weakened signals.

SUMMARY

The present invention is a system and method that facilitates efficientoptical signal beam switching. In one embodiment, a present inventioncascaded optical switching system is included in a single integratedsolution. In one exemplary implementation, the optical signal beam isdirected through “free-space” (e.g., air or glass not confined by awaveguide) by cascaded switching elements. The present inventioncascaded optical switching system and method facilitates minimization ofcumulative detrimental impacts associated with cascaded switching ofoptical signal beam. For example, a present invention cascaded opticalswitching system can “regenerate” an optical signal beam path with arealigned or corrected incidence angle. In one embodiment of the presentinvention, the corrected incidence angle facilitates shortening thecascaded switch fabric length. In one exemplary implementation, apresent invention cascaded optical switching system refocuses opticalsignal beams mitigating adverse impacts (e.g., energy loss) associatedwith diverging or spreading beams.

In one embodiment a cascaded optical switch fabric includes a pluralityof cascaded optical switches, an optical switch support member and abracing member. The plurality of cascaded optical switches form anoptical switch fabric and direct an optical signal beam from one of theplurality of optical switches to another of the plurality of opticalswitches. The optical switch support member supports the plurality ofcascaded optical switches in a cascaded configuration. The bracingmember holds the optical switch support members in a cascading positionrelative to one another forming an optical switch fabric. In oneembodiment of the present invention, an incidence corrective device isincluded in a cascaded optical switch fabric. The incidence correctivedevice comprises a variety of configurations including a variablereflective optical switch and or a variable diffraction optical switch.A corrected incidence angle permits an optical signal beam to beforwarded at a relatively shallow output angle to an optical switchlocated in a relatively close proximity on the cascading optical switchfabric. In one embodiment of the present invention, a cascaded opticalswitch fabric includes a an optical signal beam spread mitigationdevice. In one exemplary implementation, a present invention opticalsignal beam spread correction device corrects beam spreading byrefocusing the optical signal beam.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a present invention cascaded opticalswitching system.

FIG. 1B is a block diagram of an alternate embodiment in which opticalswitches are mounted on the surface of a single substrate.

FIG. 1C is a three dimensional block diagram of one embodiment of apresent invention cascaded optical switching system.

FIG. 1D is a block diagram of one exemplary implementation of a cascadedoptical switching system in which an optical signal beam is directed toa path not directly included in the cascading optical switch fabric.

FIG. 1E is a three dimensional block diagram of one exemplaryimplementation in which a cascaded optical switching system directs anoptical signal to an optical waveguide receiver that permitsbi-directional propagation of optical signal beams into or out of thecascading optical switch fabric.

FIG. 2 is a block diagram section of cascaded optical switching systemin which an optical signal beam is forwarded in two different spatialplanes.

FIG. 3A is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention in which multipleoptical signal channels are switched simultaneously.

FIG. 3B is a block diagram of one embodiment of an optical cross connectsystem including a present invention cascaded optical switching system.

FIG. 4A is a three dimensional block diagram of a dynamically variablegrating based optical switch included in one embodiment of the presentinvention.

FIG. 4B shows a cross section side view block diagram of grating from anoptical switch.

FIG. 4C illustrates a three dimensional cut-away view of the opticalswitch where the grating is shown with alternating ribbons in adeflected position relative to undeflected ribbons in accordance withone two level grating embodiment of the invention.

FIG. 4D is a block diagram illustration of a variety of two levelconfigurations for a dynamically variable grating based optical switch.

FIG. 4E is a block diagram illustration of a variety of blaze patternsfor a dynamically variable grating based optical switch.

FIG. 4F is a three dimensional block diagram of one embodiment of thepresent invention in which dynamically variable grating based opticalswitches are included in cascading topical switch fabric.

FIG. 5 is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention with a fixed incidenceangle regeneration device.

FIG. 6 is a three dimensional representation of a cascaded opticalswitching system with a fixed incidence angle regeneration device.

FIG. 7A is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention with a dynamicallyvariable incidence angle regeneration device.

FIG. 7B is a three dimensional block diagram illustration of cascadedoptical switching system, one embodiment of the present invention with adynamically variable incidence angle regeneration device.

FIG. 8A is a three dimensional block diagram of a fixed angle incidencecorrective device that also provides optical signal spread beamcorrection, one embodiment of the present invention.

FIG. 8B is a three dimensional block diagram of a dynamically variableand incidence corrective device that also provides optical signal beamspread correction, one embodiment of the present invention.

FIG. 9 is a flow chart of a cascaded optical switching method, oneembodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of theinvention, an optical switch cascading system and method with variableincidence angle correction, examples of which are illustrated in theaccompanying drawings. While the invention will be described inconjunction with the preferred embodiments, it will be understood thatthey are not intended to limit the invention to these embodiments. Onthe contrary, the invention is intended to cover alternatives,modifications and equivalents, which may be included within the spiritand scope of the invention as defined by the appended claims.Furthermore, in the following detailed description of the presentinvention, numerous specific details are set forth in order to provide athorough understanding of the present invention. However, it will beobvious to one ordinarily skilled in the art that the present inventionmay be practiced without these specific details. In other instances,well known methods, procedures, components, and circuits have not beendescribed in detail as not to unnecessarily obscure aspects of thecurrent invention.

FIG. 1A is a block diagram of cascaded optical switching system 100, oneembodiment of the present invention. Cascaded optical switching system100 includes optical switches 121, 131, 132, 141, 142, 151, 152, 171 and172 and optical switch support members 111 and 112. Optical switchsupport member 111 is coupled to switches 131, 132, 151, and 152, andoptical switch support member 112 is coupled to switches 121, 141, 142,171, and 172. In one embodiment of the present invention, the opticalswitches are coupled to support members 111 and 112 in a cascadedpattern.

The components of cascaded optical switching system 100 cooperativelyoperate to direct the propagation of an optical signal beam thoughcascaded optical switching system 100. In one embodiment, a presentinvention cascaded optical switching system is included in a singleintegrated solution. In one exemplary implementation, the optical signalbeam is directed through “free-space” (e.g., air or glass not confinedby a waveguide) by cascaded switching elements. In one exemplaryimplementation of the present invention, an optical signal beam enters apresent invention optical switch fabric and is directed along thecascaded optical switches to a particular destination (e.g., to awaveguide such as an optical cable or other optical device).

In one embodiment of the present invention, the optical switches arearranged in cascaded switching stages in which each stage includes aplurality of optical switches (e.g., a stage such as 131, 132 141, 142,151, 152, 171 and 172). In one embodiment of the present invention, theoptical switch support members 111 and 112 are cascade “boundary” planescoupled to each other by position bracing members (not shown) that holdthe optical switch support members in a position relative to oneanother. In one embodiment of the present invention, optical switchsupport members 111 and 112 are surfaces of a single substrate 188(e.g., a free space such as glass) and the optical switches are mountedin the substrate 188. FIG. 1B is a block diagram of an alternateembodiment in which the optical switches (e.g., dynamically variableoptical switches 181, 182 and 183) are mounted on the surface of asingle substrate 189.

It is appreciated that embodiments of the present invention are wellsuited for use with a variety of different types of optical switchesmounted. In one embodiment of the present invention, optical switches121, 131, 132, 141, 142, 151, 152, 171 and 172 include a reflectivecomponent and in another they include a diffractive component. Forexample, the diffractive components facilitate easier semiconductormanufacturing processes and the reflective components facilitate easieroptical manufacturing processes. The reflective components anddiffractive components may be fixed (e.g., direct an optical signal beamat a particular output angle for a given input angle) or dynamicallyvariable (e.g., direct an optical signal beam at variable output anglesfor a given input angle). In yet another embodiment of the presentinvention, optical switches 121, 131, 132, 141, 142, 151, 152, 171 and172 include a variable diffraction component (e.g., a dynamicallyvariable grating based switch). In one exemplary implementation, theoptical switches are grated light valve (GLV) switches. In someexemplary implementations, there is a combination of different types ofoptical switches included in cascaded optical switching system 100.

FIG. 1C is a three dimensional block diagram of one embodiment ofcascaded optical switching system 100. In one exemplary implementationof the present invention, cascaded optical switching system 100 directsthe propagation of optical signal beam 190 along the cascading opticalswitches 121, 131, 141, 151, and 171. In one embodiment of the presentinvention, cascaded optical switching system 100 directs optical signalbeams to various receivers for paths not directly included in thecascading path of the optical switch fabric. FIG. 1D is a block diagramof one exemplary implementation of cascaded optical switching system 100in which an optical signal beam is directed to a path not directlyincluded in the cascaded optical switch fabric. FIG. 1D shows opticalwaveguides 181 through 185 (e.g., fiber optical cables). Optical signalbeam 190 is received by cascaded optical switching system 100 fromoptical waveguide 181 (e.g., a fiber optic cable) and directed in acascaded fashion from optical switches 121 to optical switch 141 tooptical switch 151 which directs the optical signal beam out of thecascaded optical switching system 100 to optical waveguide 185.

FIG. 1E is a three dimensional block diagram of one exemplaryimplementation in which cascaded optical switching system 100 directs anoptical signal beam to an optical waveguide receiver that permitsbi-directional propagation of optical signals into or out of thecascaded optical switching system 100. Optical waveguide receiver 187 isshown coupled to optical switch support member 111. In one embodiment ofthe present invention, optical waveguide receiver 187 is a transparentmaterial that permits an optical signal beam to travel through it. Forexample, optical signal beam 190 travels though an optical waveguidereceiver (e.g., similar to waveguide receiver 187) coupled to opticalswitch support member 112 when passing through to optical waveguide 185.In one embodiment of the present invention, an optical waveguidereceiver is a hole formed by optical switch support member 111 or 112and optical signals are permitted to travel through the hole. In oneexemplary implementation of the present invention, the optical waveguidereceiver is coupled to an optical waveguide (e.g., a fiber optic cable)that directs the optical signal beam along a path different from a pathincluded in cascaded optical switching system 100.

There are a variety of cascading configuration implementations of thepresent invention cascaded optical switching system 100. In oneembodiment of the present invention, cascaded optical switching system100 directs optical signal beams to a variety of receivers or paths withdifferent spatial orientation. For example, cascaded optical switchingsystem 100 directs optical signal beams to receivers or paths in thesame spatial plane as the optical switches (e.g., see FIG. 1D) or indifferent spatial planes. FIG. 2 is a block diagram section of cascadedoptical switching system 200 in which an optical signal beam isforwarded in two different spatial planes. Cascaded optical switchingsystem 200 comprises optical switches 220 and 230, optical switchsupport members 241 and 245, position bracing member 245 and opticalwaveguide receiver 250. Optical switch support member 241 is coupled tooptical switch 220 and optical switch support member 242 is coupled tooptical switch 230. In one embodiment of the present invention, cascadedoptical switching system 200 comprises additional optical switches (notshown) upstream and downstream from optical switches 210 and 230 andposition bracing member 245 forms a reflective optical switch fabricboundary plane coupled to the optical switch support members 241 and242.

The components of cascaded optical switching system 200 cooperativelyoperate to direct the propagation of an optical signal beam thoughcascaded optical switching system 200. FIG. 2 shows optical waveguidereceiver 250 coupled to optical waveguide 251 (e.g., a fiber opticalcable) which is in a different spatial plane than the cascaded opticalswitches of cascaded optical switching system 200. Optical signal beam210 is received by cascaded optical switching system 200 and directed ina cascaded fashion to optical switch 220 which directs it to opticalswitch 230. Optical switch 230 directs optical signal beam 210 tooptical waveguide receiver 250 which forwards the optical signal beam210 to optical waveguide 251 (e.g., fiber optical cable). Opticalwaveguide 251 directs the optical signal beam 210 along a path in aspatial plane different from the cascading plane of cascaded opticalswitching system 200.

A present invention cascaded optical switching system is adaptable tomanipulate and convey a variety of different optical signals in numerousdifferent cascaded configurations. For example, a present inventioncascaded optical switching system is capable of handling a plurality ofoptical signals simultaneously. FIG. 3 is a block diagram illustrationof cascaded optical switching system 300, one embodiment of the presentinvention. In one exemplary implementation of the present invention, aplurality of optical signals are communicated in one optical signalbeam. 390 simultaneously to optical switch 310. In one exemplaryimplementation, optical signal beam 390 comprises a plurality of opticalsignals oscillating at different frequencies (e.g., different colors).Optical switch 310 directs the resulting different color optical signalbeams to different receivers or paths. For example, optical signal beam393 oscillating at a first frequency is directed along a first path(e.g., to optical switch 320) and optical signal beam 395 oscillating ata second frequency is directed along a second path (e.g., to opticalswitch 330). Directing the two optical signal beams along differentpaths facilitates different manipulation and conveyance of the signalssimultaneously. For example, optical signal beam 393 could be directedby optical switch 320 to optical waveguide 375 and optical signal beam395 could be directed by optical switch 330 along the optical switchfabric to other downstream optical switches (not shown).

In one exemplary implementation of the present invention, a reflectiveswitch is included in the cascaded optical switch fabric. In oneembodiment of the present invention, the reflective switch has areflective mirror surface and the direction it is pointing is adjustableto reflect the optical signal light beam in a different direction. Forexample, an optical signal beam hits the reflective surface at aparticular incidence angle and is reflected to a second destination(e.g., a second reflective switch included in the cascaded opticalswitch fabric). The direction the reflective surface is pointing isaltered (e.g., a mirror rotating on an axis) and the optical switchlight beam is reflected to a second destination (e.g., a thirdreflective switch included in the cascaded optical switch fabric).

A present invention cascaded optical switching system is readilyadaptable to provide a variety of functions. FIG. 3B is a block diagramof one embodiment of an optical cross connect system 390 comprising apresent invention cascaded optical switching system. In one exemplaryimplementation, an optical signal beam is directed into optical crossconnect system 390 on a fiber cable (e.g., fiber 1, fiber 2, . . . fiberN) and is directed out on another one of the fiber cables (e.g., fiber1, fiber 2, . . . fiber N).

FIG. 4A is a three dimensional block diagram of dynamically variablegrating based optical switch 10, one example of a dynamically variablegrating based optical switch. Dynamically variable grating based opticalswitch 10 is included in one embodiment of the present invention andincludes ribbon micro electromechanical machines (MEMs). In oneexemplary implementation of the present invention, dynamically variablegrating based optical switch 10 is a grating light valve switch.Dynamically variable grating based optical switch 10 utilizesdiffraction to control the direction of an optical signal. Thediffraction grating of dynamically variable grating based optical switch10 comprises multiple ribbons 30 supported in a position relative to oneanother. In one exemplary implementation multiple ribbons 30 aresupported by an integrally attached support base 20.

FIG. 4B shows a cross section side view block diagram of an exemplarygrating included in one embodiment of dynamically variable grating basedoptical switch 10. In one exemplary implementation of the presentinvention, each ribbon 30 includes a reflective planar surface 35. Theribbons of the grating are easily arranged in a variety ofconfigurations. For example, the ribbons can be arranged in a two levelpattern, a blaze pattern, a sinusoidal pattern, a triangular pattern, acombination of patterns, etc. The ribbons of grating are arranged in asingle planar configuration in FIG. 4A and FIG. 4B. FIG. 4C illustratesa three dimensional cut-away view of the optical switch where thegrating is shown with alternating ribbons in a deflected positionrelative to undeflected ribbons in accordance with one two levelembodiment of the invention (e.g., forming a square well patternswitch). A two level ribbon arrangement is one in which each ribbon islocated in one of two plans. FIG. 4D is a block diagram illustration ofa variety of two level configurations 471, 472, 473, and 474. FIG. 4E isa block diagram illustration of blaze patterns 491 and 492.

In one embodiment of the present invention, the ribbons are dynamicallyvaried. In one exemplary implementation of the present invention, theribbons are dynamically varied by selectively introducingelectromagnetic fields that deflect the ribbons. For example, amechanism for applying an electrostatic force between each ribbon andsupport base 20 is included. The position of the deflected ribbon iscontrolled by varying the strength of the applied electric field. Otherways or mechanisms for moving the ribbons relative to one another couldbe employed. In one exemplary implementation, the ribbons are supportedon their ends by slide supports which allow the ribbons to move as rigidbodies with minimal ribbon end deformation.

The configuration style and arrangement of the ribbons govern thediffraction angle of an optical signal beam. In one exemplaryimplementation of the present invention, mathematical formulas utilizedto express the behavior of a diffracted signal beam define the differentresults that are achievable with different configuration styles andarrangements. For example, the diffraction of an optical signal beam byone configuration of a two level optical switch (e.g., forming a squarewell pattern) is governed by the equations:

-   -   P=n(W+S), where P is the period or pitch, n is the number of        ribbons utilized in forming a single grating period, W is the        ribbon width, and S is the space between the ribbons; and    -   B=Arcsin((m*Y*N)±Sin A), where N=1/P or 1/(n(W+S)), B is the        diffraction angle, A is an optical signal impingement or        incidence angle, m is the order of the diffraction beam and Y is        the wavelength of the optical signal.        One example of an optical signal beam diffraction by a blaze        ribbon configuration pattern is defined by the equation:    -   B=Arcsin((m*Y*N)±sin A), where N=1/P.        For any given A and Y, the value of B can be altered for a given        order by controlling N which is done by deflecting the ribbons        and manipulating the grating period or pitch (e.g., the number        of ribbons in a period). Different ribbon deflection        configurations result in different optical signal beam        diffractions.

FIG. 4F is a three dimensional block diagram of one embodiment of thepresent invention in which dynamically variable grating based opticalswitches are included in cascading optical switch fabric. Cascadedoptical switching system 400 comprises dynamically variable gratingbased optical switches 420, 430 and 435, and optical switch supportmembers 441 and 445. Optical switch support member 441 is coupled tooptical switch 420 and optical switch support member 442 is coupled tooptical switch 430 and 435. In one embodiment of the present invention,cascaded optical switching system 400 comprises additional opticalswitches (not shown) upstream and downstream from optical switches 410and 435.

Some embodiments of a present invention cascaded optical switchingsystem facilitate optical signal beam incidence angle “correction” orrealignment. The corrected incidence angle enables a plurality ofoptical switches to be cascaded in a relatively short configuration. Forexample, the corrected incidence angle is a normal (zero) incidenceangle or near normal incidence angle in some implementations of thepresent invention. The present invention cascaded optical switchingsystem utilizes an incidence corrective device to realign the incidenceangle to produce a relatively shallow output angle. The shallow outputangle directs the optical signal beam on a path to a close opticalswitch included in the cascaded optical switch fabric.

FIG. 5 is a block diagram illustration of cascaded optical switchingsystem 500, one embodiment of the present invention with a fixedincidence angle regeneration device. Cascaded optical switching system500 includes optical switches 521, 531, 532, 541, 542, 551, 552, 571,572, 581 and 582, optical switch support members 511 and 512, andincidence corrective device 585. Optical switch support member 511 iscoupled to optical switches 531, 532, 551, 552, 581 and 582 and opticalswitch support member 512 is coupled to incidence corrective device 585and optical switches 521, 541, 542, 571, and 572. The optical switchesand optical switch support members of cascaded optical switching system500 are similar to those in cascaded optical switching system 100. Theincidence corrective device 585 receives an optical signal beam from anoptical switch (e.g., optical switch 551) at a first incidence angle anddirects it at a second output angle that is shallower than the firstincidence angle.

In one embodiment of the present invention, the incidence correctivedevice 585 directs the optical signal beam at an angle that leads it ona path normal to the base of corrective device 585 coupled to opticalswitch support member 512. In one exemplary implementation of thepresent invention, the incidence corrective device 585 directs theoptical signal beam at an angle that leads it on a path normal to anoptical switch (e.g., optical switch 581) and thereby regenerates a zeroangle of incidence at the optical switch. This enables downstreamoptical switches (e.g., optical switches 571 and 582) to be placed incloser proximity to one another in the cascaded optical switch fabric.

A present invention incidence corrective device has a number ofconfigurations and is flexibly adaptable to a number of differentimplementations. In one embodiment of the present invention, anincidence corrective device includes a fixed reflective componentoriented at a particular angle. In one exemplary implementation of thepresent invention, an incidence corrective device includes a fixedreflective component (e.g., a mirrored surface) oriented at an angledefined by one half the output angle an optical signal beam is forwardedfrom. For example, the reflective component orientation angle ofcorrective device 585 is a half of a first output angle (e.g., thetaminus one) of an optical signal beam from optical switch 551. The“regenerated” or corrected incidence angle (e.g., alpha) at which theoptical signal beam strikes the next optical switch (e.g., opticalswitch 581) is close to zero. The optical signal beam is forwarded at asecond output angle (e.g., theta) that is relatively shallow and permitsthe optical signal beam to travel on a path directed to an opticalswitch (e.g., optical switch 571) located in a relatively closeproximity on the cascading optical switch path. FIG. 6 is a threedimensional representation of a cascaded optical switching system 500with a fixed incidence angle regeneration device. In another embodiment,a fixed incidence angle regeneration device is a fresnel mirror deviceconfigured with concentric fresnel grooves.

FIG. 7A is a block diagram illustration of cascaded optical switchingsystem 700, one embodiment of the present invention with an incidencecorrective device capable of providing dynamically variable incidenceangle regeneration. Cascaded optical switching system 700 includesoptical switches 721, 731, 732, 741, 742, 751, 752, 771, 772, 781 and782, optical switch support members 711 and 712, and incidencecorrective device 787. Optical switch support member 711 is coupled toswitches 731, 732, 751, 752, 781 and 782 and optical switch supportmember 712 is coupled to incidence corrective device 787 and switches721, 741, 742, 771, and 772. The optical switches and optical switchsupport members of cascaded optical switching system 700 are similar tothose in cascaded optical switching system 100. The incidence correctivedevice 787 receives an optical signal beam from an optical switch (e.g.,optical switch 751) at a first incidence angle and directs it at asecond angle that is shallower than the output angle from a previousoptical switch. The output angle of an optical signal beam directed fromincidence corrective device 787 is dynamically variable which permitsflexible control of optical signal propagation and can direct theoptical signal beam so that it strikes a downstream optical switch at acorrected or “regenerated” incidence angle. A corrected or regeneratedincidence angle is one that assists the reduction of cumulativedetrimental effects associated with a deteriorating or deepeningincidence and output angle.

As indicated above, a present invention incidence corrective device hasa number of configurations and is flexibly adaptable to a number ofdifferent implementations. In one of the present invention, an incidencecorrective device is a dynamically variable incidence corrective device.In one exemplary implementation of the present invention, a dynamicallyvariable incidence corrective device includes a variable reflectivecomponent (e.g., a mirrored surface or a reflective optical switch)capable of being oriented or adjusted to point in a variety ofdirections. The corrected or “regenerated” incidence angle (e.g., alpha)at which the optical signal beam strikes the next optical switch isclose to zero. FIG. 7B is a three dimensional block diagram illustrationof cascaded optical switching system 700, one embodiment of the presentinvention with a dynamically variable incidence corrective device. Inone exemplary implementation, the incidence corrective device is adynamically variable grating based optical switch similar to dynamicallyvariable grating based optical switch 10.

In one embodiment, the present invention includes an optical signal beamspread mitigation device in an optical switch fabric. A presentinvention optical signal beam spread correction device corrects beamspreading by refocusing the optical signal beam. Refocusing the opticalsignal beam mitigates signal loss and facilitates efficientinterpretation of signal content.

FIG. 8A is a three dimensional block diagram of a fixed optical signalbeam spread corrective device 810, one embodiment of the presentinvention. Fixed spread corrective device 810 has a concave reflectiveface 811 that reflects the optical signal beam in a focusing pattern. Inone embodiment of the present invention, fixed optical signal beamspread corrective device 810 also reflects the optical signal beam at acorrected incidence angle. For example, an optical signal beam made upof components 821, 822 and 823 are reflected by dual spread andincidence corrective device 810 to a focal point on optical switch 830.By redirecting the components of the optical signal beam towards asingle focal point the optical signal beam is concentrated in a tighterarea. Present invention fixed spread corrective devices have a varietyof reflective face configurations for converging the beam to a tighterfocus (e.g., a concave shaped reflective face, a fresnel mirror, etc.).

FIG. 8B is a three dimensional block diagram of a spread correctivedevice 870, one embodiment of the present invention with dynamicallyvariable spread corrective capabilities that also performs spreadcorrection. Dynamically variable spread corrective device 870 forms achirped reflective face that reflects the optical signal beam in aconverging pattern. In one exemplary implementation, the dynamicallyvariable spread is a dynamically variable grating based optical switch(similar to dynamically variable grating based optical switch 10) andthe ribbons are deflected so that a chirped grating pattern is formed inwhich the periodicity gradually decreases towards the periphery. Thedeflection of the ribbons is dynamically variable and facilitatesflexible control of an optical signal. In one embodiment of the presentinvention, spread corrective device 870 performs dual spread andincidence angle correction functions.

The incidence angle correction devices and beam spread correctiondevices can include a reflective component or a diffractive componentand may be fixed or dynamically variable. In one embodiment of thepresent invention, incidence angle correction and beam spread correctionare provided by a single optical device. In one exemplaryimplementation, a dual purpose spread and incidence corrective devicecorrects incidence degeneration problems by redirecting the focusedoptical signal beam along a vector that is normal to the switchingstage. For example, spread corrective devices 810 and 870 are capable ofperforming dual spread and incidence angle correction functions. In oneembodiment of the present invention, a dual purpose corrective device isincluded in a cascading optical switch fabric in place of an incidencecorrective device (e.g., incidence corrective device 585 or 787).

FIG. 9 is a flow chart of cascaded optical switching method 900, oneembodiment of the present invention. In one embodiment of the presentinvention, cascaded optical switching method 900 includes an opticalsignal beam incidence angle regeneration process. In one embodiment ofthe present invention, cascaded optical switching method 900 includes anoptical signal beam spread corrective process.

In step 910, an optical signal beam is received by a cascaded opticalswitch fabric. In one exemplary implementation of the present inventionthe optical signal beam is introduced to a cascading optical s witchfabric from a waveguide (e.g., a fiber optic cable).

In step 920, the optical signal beam is propagated along the opticalswitch fabric. In one embodiment of the present invention, the opticalsignal beam is received by a number of optical switching points and thecontinued path direction of the optical signal beam is controlled. Inone embodiment of the present invention, the optical switching pointsare arranged in a cascaded order or configuration. In one exemplaryimplementation, optical signals are received by optical switchingpoints, including a dynamically variable grating based optical switch.

In one embodiment, cascaded optical switching method 900 includesreflecting an optical signal beam in a particular direction to anotherswitching point. In one exemplary implementation, the direction of thereflection is dynamically varied, which in turn varies the direction ofthe optical signal beam. In one embodiment, cascaded optical switchingmethod 900 includes dynamically varying the grating pitch within a lightdiffraction grating of a dynamically variable grating based opticalswitch, which in turn varies the diffraction angle of an optical signalbeam switched by the dynamically variable grating based optical switch.In one exemplary implementation of the present invention, step 920includes independently moving each ribbon of the dynamically variablegrating based optical switch in coordination with other ribbons toprovide a dynamically varying grating pitch. For example, cascadedoptical switching method 900 includes applying an electromagnetic fieldin the proximity of the ribbons which causes the ribbons to move (e.g.,deflect).

In step 930, the optical signal beam is forwarded away from the opticalswitch fabric. In one embodiment of the present invention, the opticalsignal beam is forwarded to an external waveguide (e.g., a fiber opticcable).

In one embodiment of the present invention, the optical signal beams areforwarded (“regenerated”) at a desired incidence angle to thedestination (e.g., a corrected incidence angle). In one embodiment, anincidence angle is dynamically corrected so that said optical signalbeam is forwarded at a relatively shallow output angle. In one exemplaryimplementation, the desired incidence angle is one that results in ashallow output angle. For example, the “regenerated” incidence angle(e.g., alpha) of the optical signal beam strikes the next cascadedoptical switch at an angle that is close to zero. The optical signalbeam is forwarded at a second output angle (e.g., theta) that isrelatively shallow and permits the optical signal beam to travel on apath directed to an optical switch located in a relatively closeproximity on the cascading optical switch fabric path.

In one exemplary implementation of the present invention, the opticalsignal beam is forwarded by an incidence corrective device that includesa fixed reflective component (e.g., a mirrored surface) oriented at aset angle (e.g., an angle defined by one half the output angle anoptical signal beam is forwarded from). In one exemplary implementationof the present invention, the optical signal beam is forwarded by anincidence corrective device that includes dynamically variable gratingbased optical switch ribbons deflected in a manner that propagates anoptical signal beam on a path that is normal to a cascaded secondoptical switch. In one embodiment of step 930, an optical signal beam isdirected away in a manner that corrects spread problems by refocusingthe optical signal beam in a tighter pattern.

Thus, the present invention facilitates the inclusion of a number ofswitches in a cascaded device in a manner that facilitates efficientoptical signal switching. The present invention cascaded opticalswitching system and method facilitate minimization of cumulativedetrimental impacts associated with cumulatively increasingincidence/output angles and spreading of an optical signal beam. Apresent invention cascaded optical switching system “regenerates” anoptical signal beam path with a realigned or corrected incidence angle.In one embodiment of the present invention, the corrected incidenceangle facilitates shortening the cascading optical switch fabric length.Correcting the incidence angle also facilitates utilization of opticalswitches that are economical to manufacture, however, have limitedswitching range (e.g., switch with limited reflection or diffractionmovement). In one exemplary implementation, a present invention cascadedoptical switching system refocuses spreading optical signal beams andmitigates signal loss.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

1. A cascaded optical switching system comprising: a plurality ofcascaded optical switches that form an optical switch fabric and directan optical signal beam from one optical switch of said plurality ofcascaded optical switches to another optical switch of said plurality ofcascaded optical switches while providing variable incidence anglecorrection; and an optical switch support member for supporting saidplurality of cascaded optical switches in a cascaded configuration thatis compatible with directing said optical signal beam within theboundaries of said optical switch fabric, said optical switch supportmember coupled to said plurality of cascaded optical switches.
 2. Thecascaded optical switching system of claim 1 wherein said plurality ofcascaded optical switches include dynamically variable grating basedoptical switches for diffracting said optical signal beam, wherein adiffraction angle B of said optical signal beam is governed by theequation:B=Arcsin((m*Y/(n(w+s)))±Sin A), where B is the diffraction angle, A isan optical signal incidence angle, m is the order of the diffractionbeam, Y is the wavelength of the optical signal, n is the number ofribbons utilized in forming a single grating period, W is the ribbonwidth, and S is the space between ribbons.
 3. The cascaded opticalswitching system of claim 1 wherein said plurality of cascaded opticalswitches include reflective optical switches.
 4. The cascaded opticalswitching system of claim 1 wherein said optical switch support memberincludes an optical waveguide receiver for permitting bi-directionalpropagation of optical signal beams into or out of said optical switchfabric.
 5. The cascaded optical switching system of claim 4 wherein saidoptical signal beam enters said optical switch fabric and is directed bysaid plurality of cascaded optical switches to said optical waveguidereceiver.
 6. The cascaded optical switching system of claim 1 whereinsaid plurality of cascaded optical switches are arranged in cascadedswitching stages in which each stage includes multiple cascaded opticalswitches.
 7. The cascaded optical switching system of claim 1 whereinsaid plurality of optical switches directs a plurality of opticalsignals simultaneously.
 8. A cascaded optical switch system comprising:a plurality of cascaded optical switches that form an optical switchfabric and direct an optical signal beam from one of said plurality ofcascaded optical switches to another optical switch of said plurality ofcascaded optical switches; an optical switch support member forsupporting said plurality of cascaded optical switches in a cascadedconfiguration that is compatible with directing said optical signal beamwithin the boundaries of said optical switch fabric, said optical switchsupport member coupled to said plurality of cascaded optical switches;and an incidence corrective device for realigning an incidence angle,wherein said incidence corrective device includes a dynamic componentthat controls said realigning of said incidence angle, said incidencecorrective device is coupled to said optical switch support member. 9.The cascaded optical switch system of claim 8 wherein said alignedincidence angle is a normal (zero) incidence angle.
 10. The cascadedoptical switch system of claim 8 wherein incidence corrective devicerealigns said optical signal beam so that the incidence angle saidoptical signal strikes one of said plurality of cascaded opticalswitches downstream in said optical switch fabric produces a relativelyshallow output angle.
 11. The cascaded optical switch system of claim 10wherein said relatively shallow output angle directs said optical signalbeam to one of said plurality of cascaded optical switches downstream insaid optical switch fabric, one of said plurality of cascaded opticalswitches is relatively close to said incidence corrective device. 12.The cascaded optical switch system of claim 10 wherein said incidencecorrective device receives an optical signal beam from one of saidplurality of cascaded optical switches at a first output angle anddirects it at another one of said plurality of cascaded optical switchesat a second output angle that is shallower than said first output angle.13. The cascaded optical switch system of claim 10 wherein saidincidence corrective device corrects incidence degeneration of anoptical signal.
 14. A cascaded optical switch system of claim 13 whereinsaid incidence corrective device corrects spread problems by refocusingthe optical signal beam in a tighter pattern.
 15. A cascaded opticalswitching method comprising the steps of: receiving an optical signalbeam by a cascaded optical switch fabric; propagating said opticalsignal along dynamically variable optical switches included in saidcascaded optical switch fabric; correcting an incidence angledynamically so that said optical signal beam is forwarded at arelatively shallow output angle, and forwarding said optical signal beamfrom said cascaded optical switch fabric.
 16. A cascaded opticalswitching method of claim 15 wherein said cascaded optical switch fabricis in a single plane.
 17. The cascaded optical switching method of claim15 further comprising the steps of: receiving said optical signal beamby an optical switch included in said cascaded optical switch fabric;and forwarding said optical signal beam from said optical switchincluded in said cascaded optical switch fabric.
 18. The cascadedoptical switching method of claim 17 wherein said optical signal beam isreceived by said optical switch at an incidence angle and is forwardedat a dynamically adjustable shallower output angle.
 19. The cascadedoptical switching method of claim 18 wherein the incidence angle isadjusted so that the output angle forwards the optical signal to anotheroptical switch included in said cascaded optical switch fabric at arelatively close location.
 20. The cascaded optical switching method ofclaim 15 further comprising the step of correcting cumulative spreadimpacts on said optical signal beam.
 21. A cascaded optical switchingsystem comprising: a plurality of cascaded optical switches that form anoptical switch fabric and direct an optical signal beam from one opticalswitch of said plurality of cascaded optical switches to another opticalswitch of said plurality of cascaded optical switches while providingvariable incidence angle correction, wherein said plurality of cascadedoptical switches include dynamically variable grating based opticalswitches for diffracting said optical signal beam, wherein a diffractionangle B of said optical signal beam is governed by the equation:B=Arcsin((m*Y/(n(w+s)))±Sin A),  where B is the diffraction angle, A isan optical signal incidence angle, m is the order of the diffractionbeam, Y is the wavelength of the optical signal, n is the number ofribbons utilized in forming a single grating period, W is the ribbonwidth, and S is the space between the ribbons; and an optical switchsupport member for supporting said plurality of cascaded opticalswitches in a cascaded configuration that is compatible with directingsaid optical signal beam within the boundaries of said optical switchfabric, said optical switch support member coupled to said plurality ofcascaded optical switches.